| use std::fmt; |
| |
| use downcast_rs::impl_downcast; |
| |
| use super::Weight; |
| use crate::core::searcher::Searcher; |
| use crate::query::Explanation; |
| use crate::schema::Schema; |
| use crate::{DocAddress, Term}; |
| |
| /// Argument used in `Query::weight(..)` |
| #[derive(Copy, Clone)] |
| pub enum EnableScoring<'a> { |
| /// Pass this to enable scoring. |
| Enabled(&'a Searcher), |
| /// Pass this to disable scoring. |
| /// This can improve performance. |
| Disabled(&'a Schema), |
| } |
| |
| impl<'a> EnableScoring<'a> { |
| /// Returns the schema. |
| pub fn schema(&self) -> &Schema { |
| match self { |
| EnableScoring::Enabled(searcher) => searcher.schema(), |
| EnableScoring::Disabled(schema) => schema, |
| } |
| } |
| |
| /// Returns true if the scoring is enabled. |
| pub fn is_scoring_enabled(&self) -> bool { |
| match self { |
| EnableScoring::Enabled(_) => true, |
| EnableScoring::Disabled(_) => false, |
| } |
| } |
| } |
| |
| /// The `Query` trait defines a set of documents and a scoring method |
| /// for those documents. |
| /// |
| /// The `Query` trait is in charge of defining : |
| /// |
| /// - a set of documents |
| /// - a way to score these documents |
| /// |
| /// When performing a [search](Searcher::search), these documents will then |
| /// be pushed to a [`Collector`](crate::collector::Collector), |
| /// which will in turn be in charge of deciding what to do with them. |
| /// |
| /// Concretely, this scored docset is represented by the |
| /// [`Scorer`] trait. |
| /// |
| /// Because our index is actually split into segments, the |
| /// query does not actually directly creates [`DocSet`](crate::DocSet) object. |
| /// Instead, the query creates a [`Weight`] object for a given searcher. |
| /// |
| /// The weight object, in turn, makes it possible to create |
| /// a scorer for a specific [`SegmentReader`]. |
| /// |
| /// So to sum it up : |
| /// - a `Query` is a recipe to define a set of documents as well the way to score them. |
| /// - a [`Weight`] is this recipe tied to a specific [`Searcher`]. It may for instance |
| /// hold statistics about the different term of the query. It is created by the query. |
| /// - a [`Scorer`] is a cursor over the set of matching documents, for a specific |
| /// [`SegmentReader`]. It is created by the [`Weight`]. |
| /// |
| /// When implementing a new type of `Query`, it is normal to implement a |
| /// dedicated `Query`, [`Weight`] and [`Scorer`]. |
| /// |
| /// [`Scorer`]: crate::query::Scorer |
| /// [`SegmentReader`]: crate::SegmentReader |
| pub trait Query: QueryClone + Send + Sync + downcast_rs::Downcast + fmt::Debug { |
| /// Create the weight associated with a query. |
| /// |
| /// If scoring is not required, setting `scoring_enabled` to `false` |
| /// can increase performances. |
| /// |
| /// See [`Weight`]. |
| fn weight(&self, enable_scoring: EnableScoring<'_>) -> crate::Result<Box<dyn Weight>>; |
| |
| /// Returns an `Explanation` for the score of the document. |
| fn explain(&self, searcher: &Searcher, doc_address: DocAddress) -> crate::Result<Explanation> { |
| let weight = self.weight(EnableScoring::Enabled(searcher))?; |
| let reader = searcher.segment_reader(doc_address.segment_ord); |
| weight.explain(reader, doc_address.doc_id) |
| } |
| |
| /// Returns the number of documents matching the query. |
| fn count(&self, searcher: &Searcher) -> crate::Result<usize> { |
| let weight = self.weight(EnableScoring::Disabled(searcher.schema()))?; |
| let mut result = 0; |
| for reader in searcher.segment_readers() { |
| result += weight.count(reader)? as usize; |
| } |
| Ok(result) |
| } |
| |
| /// Extract all of the terms associated with the query and pass them to the |
| /// given closure. |
| /// |
| /// Each term is associated with a boolean indicating whether |
| /// positions are required or not. |
| /// |
| /// Note that there can be multiple instances of any given term |
| /// in a query and deduplication must be handled by the visitor. |
| fn query_terms<'a>(&'a self, _visitor: &mut dyn FnMut(&'a Term, bool)) {} |
| } |
| |
| /// Implements `box_clone`. |
| pub trait QueryClone { |
| /// Returns a boxed clone of `self`. |
| fn box_clone(&self) -> Box<dyn Query>; |
| } |
| |
| impl<T> QueryClone for T |
| where T: 'static + Query + Clone |
| { |
| fn box_clone(&self) -> Box<dyn Query> { |
| Box::new(self.clone()) |
| } |
| } |
| |
| impl Query for Box<dyn Query> { |
| fn weight(&self, enabled_scoring: EnableScoring) -> crate::Result<Box<dyn Weight>> { |
| self.as_ref().weight(enabled_scoring) |
| } |
| |
| fn count(&self, searcher: &Searcher) -> crate::Result<usize> { |
| self.as_ref().count(searcher) |
| } |
| |
| fn query_terms<'a>(&'a self, visitor: &mut dyn FnMut(&'a Term, bool)) { |
| self.as_ref().query_terms(visitor); |
| } |
| } |
| |
| impl QueryClone for Box<dyn Query> { |
| fn box_clone(&self) -> Box<dyn Query> { |
| self.as_ref().box_clone() |
| } |
| } |
| |
| impl_downcast!(Query); |